Campus Units

Chemistry, Biochemistry, Biophysics and Molecular Biology

Document Type

Article

Publication Version

Published Version

Publication Date

8-6-2003

Journal or Book Title

Journal of Physical Chemistry B

Volume

107

Issue

34

First Page

9122

Last Page

9127

DOI

10.1021/jp030106r

Abstract

The picosecond NO geminate rebinding kinetics of wild-type leghemoglobin, a monomeric plant hemoglobin with structural similarity to myoglobin, and six mutant proteins at the distal histidine (H61G, H61A, H61V, H61L, H61R, H61F) are investigated. All of the mutant proteins yield rebinding kinetics that are initially more rapid than that of the wild-type protein. At long times, the rebinding of H61F becomes slower than that of wild-type leghemoglobin. The H61V, H61L, and H61G mutant proteins give extraordinarily rapid and complete geminate rebinding. On a 40 ps time scale, distal effects are overwhelmingly evident for all of the mutants considered. That binding is both rapid and, in several cases, essentially single-exponential is suggestive of the nature of the barrier induced by the distal modification:  it must be such that the ligand is prohibited from reorienting with respect to, and diffusing sufficiently far from, the heme iron so that a distribution of return paths is not offered to it. Over the past 20 years, the relative importance attributed to the proximal and the distal sides in modulating geminate ligand binding has varied considerably. Our results with leghemoglobin are discussed in terms of the relative contributions of proximal and distal effects to geminate rebinding kinetics.

Comments

Reprinted (adapted) with permission from Journal of Physical Chemistry B 107 (2003): 9122, doi:10.1021/jp030106r. Copyright 2003 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

Share

COinS